Conduit fitting with pull-up indication

ABSTRACT

A fitting for a tube or pipe capable of functioning a high pressures having a first fitting component adapted to receive the conduit end; a conduit gripping device such as a ferrule or ferrules and a second fitting component that can be joined to the first fitting component to cause the conduit gripping device to grip the conduit and seal when assembled. In one aspect of the invention, the first fitting component is constructed from a material that is softer than the material used to construct the second fitting component. An additional aspect of the invention include a retaining portion on the second fitting component that constrains the tube gripping device against pressure. The retaining portion can also be configured to retain the tube gripping device to the second fitting component prior to installation and in a finger-tight condition. A further aspect of the invention includes a first fitting component in which an exterior portion of the component is work hardened radially outward from the tube gripping device. The fitting may optionally be provided with a structure to effect the pull-up by torque functionality.

RELATED APPLICATIONS

This application is a continuation application of U.S. Ser. No.13/860,763, filed Apr. 11, 2013, titled CONDUIT FITTING WITH RADIALCONSTRAINT, which is a continuation of U.S. application Ser. No.12/718,180, filed Mar. 5, 2010, titled CONDUIT FITTING WITH PULL-UPINDICATION which is a continuation of U.S. application Ser. No.11/112,800 filed on Apr. 22, 2005 for FITTING FOR TUBE AND PIPE, nowissued U.S. Pat. No. 7,695,027, which claims the benefit of U.S.provisional patent application Ser. Nos. 60/564,358 for HARDENED TUBEFITTING filed Apr. 22, 2004 and 60/633,885 for FITTING FOR TUBE AND PIPEfiled Dec. 7, 2004, the entire disclosures of which are fullyincorporated herein by reference.

BACKGROUND OF THE INVENTION

Flareless fittings have been in use for decades for conduits such astubes and pipes. A flareless fitting is used to connect or join two tubeor pipe ends or to connect a conduit end to another assembly such as atank, a valve, a manifold and so on. The applications are as varied asthe types of assemblies with which the fittings are used. One verycommon type of flareless fitting is a ferrule type fitting. In a ferruletype fitting, one or more ferrules are used to join or connect a conduitend to a fitting member, typically called a fitting body. The fittingbody may then be joined to (or be part of) another assembly. In aferrule type fitting, the ferrule or ferrules must establish a fluidtight seal, particularly under pressure, as well as adequate grip of theconduit and protection against vibration fatigue. High performancefittings, such as are available from Swagelok Company, Solon, Ohio, arecapable of withstanding pressures many times the rated pressure of thefitting without leaking, without vibration fatigue and without conduitblow out to the point that the conduit will burst before a seal iscompromised or the ferrule(s) can lose their grip on the conduit.

Ferrule style fittings have an advantage over other end connections inthat they do not rely on any special preparation of the tube or pipeend, other than low cost squaring and deburring. This is because theferrules create the seals and tube grip.

Flareless fittings that use ferrules are commonly used in sophisticatedchemical processing apparatus because of their high reliability. Forexample, in the semiconductor industry, such fittings assure containmentof expensive or toxic chemicals. Typically, these applications are highpurity and therefore, rely on conduits made of stainless steel or otherlow corrosion, high strength alloys.

Lower cost markets, such as the automotive industry, have their ownperformance requirements for fluid connections. Most notably, automotiveassembly requires simpler assembly procedures. The automotive industryhas resisted using ferrule type fittings not only for cost reasons, butalso for assembly needs. Ferrules are fairly small annular members thatcan be dropped or lost in low cost, high throughput facilities. Typicalferrule type fittings are also assembled by what is commonly known aspull-up by turns. Two threaded components, such as a nut and body,enclose the conduit end and one or more ferrules. The assembly is firsttightened to a finger tight condition and then a prescribed number ofturns, such as one and a quarter or one and a half turns, are used topull-up the fitting to its final assembled condition. The number ofturns is carefully prescribed to prevent over torque or inadequatepull-up. The automotive industry on the other hand typically wants toassemble parts by torque. This allows a simple torque wrench or tool tobe used to make the final assembly with the assurance that the fittinghas been properly assembled.

The next generation of motor vehicles, especially for passenger use,will likely be in the area of alternative fuels such as high pressurehydrogen. The pressure ratings that will be required significantlyexceed current rated pressure for ferrule type, flareless fittings(although not the pressure capability of high performance ferrule type,flareless fittings.) For example, it is expected that gaseous hydrogenwill need to be contained at a pressure of 15,000 psi (15 ksi). Currentflareless tube fittings are rated below 10 ksi.

For current high pressure flareless fittings, the material used for thefluid components of the fitting, in at least some applications, must behardened. To this end, the block of material from which the fitting bodyis made may be a material hardened by heat treating or, in the exampleof an austenite stainless steel, may be manufactured from work hardenedbar stock. For a straight union fitting, manufacturing the fitting fromwork hardened bar stock is suitable. More complex configurations, suchas elbows and tee shapes, however, require substantially larger blocksof material. For these types of fittings, a substantial amount ofmaterial must be removed, which can drive up manufacturing costs.

Some threaded tube fittings, on the other hand are made from compactforgings which save material and cost. The use of forged fittingcomponents is well accepted for low pressure applications. The forgingprocess, however, can cause material annealing which eliminates anyprior work hardening. Thus, forged components are typically unsuitablefor high pressure applications.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a fitting is providedthat will perform at a high pressure rating without compromisingleakage, grip and vibration performance achieved by earlier two ferruletube fittings, even while in some embodiments using lower costmanufacturing processes and materials. In one embodiment, a male fittingcomponent, such as a nut, includes a structure, which constrains a tubegripping device, such as a ferrule or ferrules. As a result, the matingfemale fitting component need not be formed from a hardened material.The invention thus provides, in accordance with additional aspects, ahigh pressure fitting that utilizes a fitting body of one material, witha mating nut that is made of a harder material. For example, the bodymay be annealed stainless steel and the nut may be work hardenedstainless steel. This combination can be used in higher pressureapplications that can have rated pressures greater than 8 ksi, evengreater than 12 ksi. This in part arises from the use of a nut that hasa hardness ratio relative to the body of about 1.3:1 to about 2:1(Vickers scale) or greater. In another embodiment, the ferrules are casehardened, for example by a low temperature carburization process toprovide very hard ferrules. In another embodiment, the nut provides asecondary pressure seal against a surface of the fitting body.

In accordance with another aspect of the invention, a fitting isprovided with a first component that has a portion adapted to constraina tube gripping device where the exterior of the component is workhardened, for example, in the area of radial constraint. In oneembodiment, a selected portion of the fitting is work hardened, forexample the female fitting component, by plastically deforming thematerial on an exterior portion or surface of the female fittingcomponent. Because the selected portion is work hardened, the femalefitting component can be initially made from a non-hardened material byforging or casting. In another embodiment, the work hardening provides amore useful configuration to the fitting. For example, the workhardening can include an external thread convolution that allows thefitting to connect with another device or structure. The invention alsorelates to a method of selectively work hardening, such as by rollingcircumferential ridges or threads, for example, on a female threadedfitting component, that may be made initially as a forging.

In accordance with another aspect of the invention, a ferrule type,flareless fitting is provided that can optionally be pulled-up to itsfinal assembled condition by torque rather than by turns. In oneembodiment, a male fitting component, such as a nut, includes astructure having a surface that engages a surface on a female fittingcomponent to facilitate pull-up by torque. In another embodiment, aferrule is provided with a flange that engages a surface on a femalefitting component to facilitate pull-up by torque. In yet anotherembodiment, the nut includes an external surface, for example a surfaceof a tool engaging portion, that engages an exterior surface on afitting body.

In accordance with another aspect of the invention, a ferrule typeflareless fitting is provided that allows for easy installation byproviding a single assembly that has one or more ferrules held with afitting component. In one embodiment, a cartridge nut assembly allowsone or more ferrules to be retained securely on a fitting componentprior to installation so that the ferrules and the fitting componentwill not become separated prior to installation. In another embodimentof the invention, a tool is provided which retains the one or moreferrules onto a fitting component prior to installation and is removablyduring assembly.

The invention also provides a fitting with an annealed female body and amale hardened nut in combination with the pull-up by torquefunctionality. The invention also provides a fitting with pull-up totorque functionality in combination with the functionality of a nut thatretains one or more ferrules in an uninstalled condition. The inventionalso provides a fitting with pull-up to torque functionality incombination with the functionality of the nut forming a seal against thebody. The invention also provides a fitting with a female threaded bodyhaving at least two tapered or camming surfaces.

In accordance with another aspect of the invention, a ferrule typeflareless fitting is provided that includes a male nut that is flushwith the body or recessed in the body when the fitting is in a pulled-upcondition. In one embodiment, a keyed male nut, and corresponding keytool, is provided that has a hex area removed to reduce its overalllength.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the present invention will become apparent toone skilled in the art to which the present invention relates uponconsideration of the following description of the invention withreference to the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-section of an exemplary embodiment of afitting in accordance with the present invention;

FIGS. 1A, B, and C illustrate different thread options for the fittingcomponents of the exemplary fitting shown in FIG. 1;

FIG. 2 is an enlarged cross section of a first ferrule of the exemplaryfitting shown in FIG. 1;

FIG. 3 is an enlarged cross section of a second ferrule of the exemplaryfitting shown in FIG. 1;

FIG. 4 is a cross section of a nut of the exemplary fitting shown inFIG. 1;

FIG. 5 is a cross section of the nut of FIG. 5, enlarged in the area ofthe cartridge;

FIG. 6 is a cross section of a body of the exemplary fitting shown inFIG. 1;

FIG. 7 is a half longitudinal cross-section of the exemplary fittingshown in FIG. 1 in a finger tight condition, enlarged in the area of theferrule;

FIG. 8 is a half longitudinal cross-section of the exemplary fittingshown in FIG. 1 in a pulled-up condition, enlarged in the area of theferrule;

FIG. 9 is a graph of illustrative data for torque versus nutdisplacement for the exemplary fitting shown in FIG. 1;

FIG. 10 is a longitudinal cross section of the nut and two ferrules ofthe exemplary fitting shown in FIG. 1 where nut and two ferrules areinstalled on a tool;

FIG. 11 is a perspective view of the tool shown in FIG. 10;

FIGS. 12A-B are side cross-sectional views of the exemplary fittingshown in FIG. 1 illustrating various steps in the use of the tool formaking-up the fitting;

FIG. 13 is a longitudinal cross-section of another exemplary fitting ofthe present invention shown in a finger tight condition;

FIG. 14 is a half longitudinal cross-section of the exemplary fittingshown in FIG. 13 in a pulled-up condition, enlarged in the area of theferrule;

FIG. 15 is a cross section of a nut of the exemplary fitting shown inFIG. 13;

FIG. 16 is a cross section of the nut of FIG. 15, enlarged in the areaof the cartridge;

FIG. 17 is an enlarged cross section of a first ferrule of the exemplaryfitting shown in FIG. 13;

FIG. 18 is an enlarged cross section of a second ferrule of theexemplary fitting shown in FIG. 13;

FIG. 19 is a longitudinal cross-section of another exemplary fitting ofthe present invention shown in a finger tight condition;

FIG. 20 is a half longitudinal cross-section of the exemplary fittingshown in FIG. 19 in a pulled-up condition, enlarged in the area of theferrule;

FIG. 21 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in the finger tight condition;

FIGS. 22A and 22B are plan and elevation views of a key tool for usewith the exemplary fitting shown in FIG. 21;

FIG. 23 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in the pulled-up condition;

FIG. 24 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in a finger tight condition,enlarged in the area of the ferrule;

FIG. 25 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in a finger tight condition,enlarged in the area of the ferrule.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is described herein with specific reference to avariety of structural and material features, such descriptions areintended to be exemplary in nature and should not be construed in alimiting sense. For example, the exemplary embodiments are describedprimarily in terms of a stainless steel tube fitting for automotiveapplications. Those skilled in the art, however, will readily appreciatethat any one or more of the aspects and features of the invention may beused outside of the automotive industry, can be used with materialsother than stainless steel and can be used with many conduits including,but not limited to, tube or pipe. Moreover, many of the aspects of theinvention may be used for lower pressure fittings, or the higher ratedpressure concepts disclosed herein may be used in a fitting even whenthe fitting itself will be used in a lower pressure application. Stillfurther, the exemplary embodiments herein illustrate what is commonlyknown as a female-style fitting, meaning that a female (i.e. internally)threaded component receives and abuts the conduit end. Many aspects ofthe invention will find application in male-style fittings as will beapparent to those skilled in the art. The invention will also findapplication for fitting assemblies that do not require threadedconnections between the fitting components, for example clamped orbolted fittings may be used. The invention will also find applicationfar beyond the exemplary embodiments herein as to connections that canbe made to a wide and ever expansive variety of fluid componentsincluding, but not limited to, other conduits, flow control devices,containers, manifolds and so on.

While various aspects of the invention are described and illustratedherein as embodied in combination in the exemplary embodiments, thesevarious aspects may be realized in many alternative embodiments, eitherindividually or in various combinations and sub-combinations thereof.Unless expressly excluded herein all such combinations andsub-combinations are intended to be within the scope of the presentinvention. Still further, while various alternative embodiments as tothe various aspects and features of the invention, such as alternativematerials, structures, configurations, methods, devices, software,hardware, control logic and so on may be described herein, suchdescriptions are not intended to be a complete or exhaustive list ofavailable alternative embodiments, whether presently known or laterdeveloped. Those skilled in the art may readily adopt one or more of theaspects, concepts or features of the invention into additionalembodiments within the scope of the present invention even if suchembodiments are not expressly disclosed herein. Additionally, eventhough some features, concepts or aspects of the invention may bedescribed herein as being a preferred arrangement or method, suchdescription is not intended to suggest that such feature is required ornecessary unless expressly so stated. Still further, exemplary orrepresentative values and ranges may be included to assist inunderstanding the present invention however, such values and ranges arenot to be construed in a limiting sense and are intended to be criticalvalues or ranges only if so expressly stated.

Although various embodiments are described herein with specificreference to the fitting components being made of stainless steel, suchdescription is intended to be exemplary in nature and should not beconstrued in a limiting sense. Those skilled in the art will readilyappreciate that the invention may be realized using any number ofdifferent types of metals material for the fitting components, as wellas metal tubing materials, including but not limited to 316, 316L, 304,304L, any austenitic or ferritic stainless steel, any duplex stainlesssteel, any nickel alloy such as HASTALLOY, INCONEL, MONEL, alloy 825,alloy 625, any precipitation hardened stainless steel such as 17-4PH forexample, brass, copper alloys, any carbon or low allow steel such as12L14 steel for example. An important aspect of the choice of materialsis that the tube gripping device preferably should be case or throughhardened to a ratio of at least 3.3 and preferably 4 or more timesharder that the hardest tubing material that the fitting will be usedwith. Therefore, the tube gripping device need not be made of the samematerial as the tubing itself. For example, the tube gripping device maybe selected from the stainless steel material noted above, or othersuitable materials that can be case hardened, such as magnesium,titanium and aluminum, to name some additional examples.

With reference to FIG. 1, the fitting 10 includes a first fittingcomponent 12 that can be realized in the form of a female threaded bodyhaving internal threads 14. The first fitting component 12 joins orconnects with a second fitting component 16 that can be realized in theform of a male threaded nut having external threads 18 that threadablymate with the threads 14 of the first component 12 when the fitting 10is made-up or assembled. Different thread options and non-threadedcoupling designs may be used for the first and second fittingcomponents.

FIGS. 1A, B and C illustrate different thread options for a threadedcoupling between the body 12 and nut 16. FIG. 1A illustrates 30° fromnormal (i.e. 60 degrees included angle) symmetrical thread flanks 19 aand 19 b. FIG. 1B illustrates the optional use of a buttress threaddesign in which the thread flanks are asymmetrical with one flank 19 atypically in the range of about 45 degrees and the adjacent flank in therange of about 3 degrees to about 7 degrees from normal. The buttressthread design provides high strength loading on one side to help reduceflaring of the nut during high torque assembly and in high pressureapplications. FIG. 1C illustrates the use of acme threads wherein theflanks again are symmetrical but of a steeper angle such as about 3degrees to about 7 degrees from normal. The acme thread design provideshigher strength loading uniformly compared to the 60 degrees threads.

The fitting 10 further includes a tube gripping device. Ferrules are anexample of a tube gripping device and, in this example, two ferrules areincluded; a front or first ferrule 20 and a back or second ferrule 22.The fitting, however, can be designed for using a single ferrule oralternative tube gripping device. The nut 16 and ferrules 20, 22 fitonto a conduit end T that is received by the body 12.

FIG. 2 is an enlarged cross section of a first or front ferrule of theexemplary fitting shown in FIG. 1. The first ferrule 20 is a generallyannular part with a generally cylindrical interior wall 24 that slipsover the outer surface S of the tube end T (see FIG. 1). The firstferrule 20 has an outer surface 26 that tapers outwardly in a generallyconical manner from a forward portion 28 to a rearward portion 30. Theforward portion 28 may include a sharp front edge 32 and a rounded noseportion 34. The rearward portion 30 includes a frusto-conical recess 36that forms a camming surface 38. The tapered outer surface 26 mayconverge to an axially aligned flange 40 (wherein the axis X is thecentral longitudinal axis of the conduit and the fitting 10).

FIG. 3 is an enlarged cross section of a second or back ferrule of theexemplary fitting shown in FIG. 1. The second ferrule 22 is a generallyannular part with a generally cylindrical interior wall 42 that slipsover the outer surface S of the tube end T (see FIG. 1). The secondferrule 22 further includes a nose portion 46 and an axially extendingouter surface 44 that extends about a rearward portion 48 of theferrule. The nose portion 46 includes a sharp front edge 50 and a firsttapered portion 52 that extends toward the rear portion 48 from thesharp edge 50 at a rake angle α of about fifteen degrees, for example.The first tapered portion 52 merges or blends to a second taperedportion 54 along a first curved portion 56 such as a radius, forexample. The second tapered portion 54 merges or blends to the axialportion 44 at a corner or edge 58 which may alternatively be a radius.The second tapered portion 54 extends at an angle β, such as aboutthirty-five degrees, for example.

The second ferrule 22 further includes a back end portion 60 that has adriven surface 62. The driven surface 62 extends radially outwardly atan angle δ, such as about five degrees (referenced from normal to theaxis X), for example. The driven surface 62 merges or blends with theaxial portion 44 along a second curved portion 64.

FIGS. 4-5 illustrate a cross section of a nut of the exemplary fittingshown in FIG. 1. The nut 16 has an overall cylindrical configurationdefining a central bore 66 that receives the tube end T during assembly.The nut 16 has a front end 68 that defines a socket, recess or cage 70.The socket 70 is defined by a cylindrical first portion 72 and afrusto-conical portion 74 that tapers radially inwardly towards a backend 75 of the nut 16. The frusto-conical portion 74 forms a drivesurface that contacts the driven surface 62 of the second or backferrule during pull-up. The drive surface 74 is formed at an angle τ,such as about fifteen degrees, for example. Because the angle τ isdifferent from the angle δ, the driven surface 62 of the back ferrule 22initially contacts the drive surface 74 at the outer radius 64 (see FIG.7). The difference angle Φ, where Φ=τ−δ, assures that the initialcontact between the nut 16 and the second ferrule 22 is radially spacedfrom the tube end T; thus, the contact between the driven and the drivesurfaces 62, 74 is not a flush.

The socket 70 is formed within an axially extending and generallycylindrical wall or cartridge 76. The cartridge 76 is sized to retainthe back ferrule 22 and at least a portion of the rearward portion 30 ofthe front ferrule 20 therein, to form a nut and ferrule assembly orcartridge nut assembly 78 (see FIG. 10). The term cartridge as usedherein is a shorthand reference to the concept of a fitting component,in this example a male threaded nut 16 having a structure that canretain one or more ferrules therewith even when the assembly isuninstalled with the mating fitting component. Thus, the cartridge nutassembly 78, which includes the cartridge nut 16 and one or moreferrules 20, 22, may be used to retain the ferrules and nut togetherwhen the assembly is either uninstalled or only installed in the body 12in a finger tight condition.

Many different techniques may be used to retain the ferrule or ferrules20, 22 within the cartridge nut 16 prior to final pull-up or eveninitial assembly into the mating fitting component. For example, anon-contaminating glue or adhesive may be used to hold the ferrules 20,22 in place, with the glue releasing its grip under the force ofpull-up. Alternatively, the cartridge wall 76 may be slightly crimpedradially inwardly to retain the ferrules 20, 22 therein. Still further,an adhesive may be used that breaks down into a lubricant upon pull-upto help reduce pull-up torque. In another embodiment disclosed herein, atool is used to hold the parts together as an assembly 78 (see FIG. 10).

With reference to FIG. 5, the cartridge 76 may include a tapered portion82 that tapers radially outwardly towards the back end 75 of the nut 16.The tapered portion 82 extends at an angle θ, such as for example aboutforty-five degrees.

The nut 16 further includes a tool engagement portion 80 that allows atorque wrench or other tool to be used to tighten and pull-up thefitting 10. The tool engagement portion 80 in the exemplary embodimentof FIG. 1 is realized as a hex portion 80. The tool engagement portion80 can be found in variety of ways. For example, the nut 16 may includea key hole that allows a corresponding keyed wrench to be used totighten and pull-up the fitting, as described in relation to FIGS.21-22.

The nut 16 may further include a neck 77 of somewhat reduced outerdiameter between the threads 18 and the tool engagement portion 80. Theneck 77 may be used to provide an intrinsic gauging function to verifyproper pull-up for both pull-up by torque and pull-up by turns. Byintrinsic gauging is meant a structure or feature associated with thefitting itself (as contrasted with a separate tool or gauge) thatprovides an indication to the assembler that the fitting has beenproperly assembled and pulled up. A large variety of structures orfeatures can perform the intrinsic gauging function, some examples ofwhich are disclosed in International Application No. 03/07739 and U.S.patent application Ser. No. 10/711,353, and U.S. Pat. No. 6,640,457 B2,the entire disclosures of which are fully incorporated herein byreference. A gap gauge may also be used in a known manner to confirmproper pull-up of the fitting 10.

With reference to FIG. 6, the female threaded body 12 is a generallycylindrical part centered on the axis X. The body 12 has an opening 83at a forward end 84 adapted to receive the tube end T. A central bore 86extends through the body 12 and forms a port 88 which defines a fluidflow path. The port 88 may be used to establish fluid communication withanother part such as a valve, tee, elbow, manifold, etc. It should benoted that although the female threaded fitting component 12 is shown asa separate stand alone part, the features of the component by which itcan make a fluid connection with the male threaded fitting componentcould, alternatively, be incorporated into a bulk body 85 such as amanifold, valve, pump, tank, and so on, commonly referred to as a fluidport.

The female body further includes a counterbore 89 that forms a shoulder90. The tube end T bottoms against the shoulder 90 when received by thebody 12. The counterbore 89 may have a slight taper to it to help form aseal about the tube end T upon pull-up of the fitting 10.

The female fitting component 12 further includes a first taperedsurface, such as for example frusto-conical surface 92 and a secondtapered surface, such as for example frusto-conical surface 94. Thefirst frusto-conical surface 92 forms a first or ferrule camming surfacein the body 12 and may be axially adjacent the forward end of thecounterbore 89. The second frusto-conical surface 94 forms a second orcartridge camming surface in the body 12 and may be axially adjacent ornear the forward end of the first camming surface 92. The first orferrule camming surface is formed at an angle σ. The angle σ may beselected to optimize the camming action with the nose portion 34 of thefirst ferrule 20. In typical two ferrule and one ferrule fittings, thisangle is about twenty degrees but may be any suitable value from about10 degrees to about forty-five degrees.

The second or cartridge camming surface 94 is formed at an angle ρ. Inthis example, the angle is about forty-five degrees, but this angle isnot required. The angles σ and ρ may be the same or different from eachother. In the illustrations herein, the angles are different, thereforethere is a radial step 96 that joins the two camming surfaces 92, 94.This step may be radial or may have its own angle or taper or otherprofile as needed.

The body 12 further includes female threads 14 which threadably matewith the threads 18 on the male nut 16. It should be noted that the body84 may also be formed into a cap by closing off or eliminating the port86, such as for example can be used to cap the end of a fluid line. Thebody 12 may be provided with hex flats to facilitate holding the bodywhile the nut 16 is being tightened down during pull-up. Of course,pull-up involves relative axial translation between the fittingcomponents, the nut 16 and body 12, in this case effected by relativerotation between the nut and body, regardless of which fitting componentis being held and which is being turned. In a non-threaded coupling,pull-up involves relative axial translation between the two fittingcomponents by means other than two threaded components, such as forexample two components forced together by a clamping device.

The body 12 may also include a work hardened portion 81 formed generallyradially outward of the ferrules 20, 22. In addition to being radiallyoutward of the tube gripping device 20, 22, the amount and location ofwork-hardening can be selected, as appropriate, for a given application.The work hardened portion preferably extends from the forward end 84 ofthe fitting body 12 to at least a location radially outward of theradial step 96. The work hardening portion, however, may extend, forexample, to a location radially outward of the rearward end of the firstcamming surface 92 or extend the entire length of the exterior surfaceof the body 12. The work hardening is accomplished by plasticallydeforming the material on an exterior portion of the fitting component12. The material can be plastically deformed in a variety of ways. Forexample, the work hardening may be accomplished by creating a series ofgenerally rolled circumferential ribs or by rolling an exterior malethread 98 on the fitting body 12.

FIGS. 7 and 8 illustrate the fitting 10, enlarged in the area of theferrules, in a finger tight condition and a pulled-up condition,respectively. In the finger tight condition of FIG. 7, the first orfront ferrule nose portion 28 is positioned partially within the cammingmouth formed by the ferrule camming surface 92. Note that the backferrule 22 engages the drive surface 74 of the nut 16 at the differenceangle Φ. This assures that during pull-up the back end portion 60 of thesecond ferrule 22 will move or remain radially outward from the outersurface S of the tube end T. At the same time, the nose portion 46 ofthe back ferrule 22 is plastically deformed so that the sharp edge 50bites or indents into the tube surface S, producing a strong tubegripping shoulder 100 and a fluid tight seal. The ferrule nose 46 alsohinges so that a portion 102 of the cylindrical wall 42 is radiallycompressed against the tube wall surface S to swage or collet the backferrule 22 against the surface axially spaced from the bite 100. Thisregion of high radial compression and collecting of the back ferrule 22provides excellent protection of the bite or indent 100 from vibration.The back ferrule 22 thus is designed to hinge in deformation and effectupon pull-up the collecting region 102 between the bite or indent 100and the back end 60 of the ferrule while having the back end portion 60moved radially outward or kept radially outward from the outer surface Sof the tube end T. The exact location of the collecting region 102 willbe determined by, among other things, the size of the ferrule 22. Insome cases, the collet region 102 can be adjacent the bite or indent 100while in other cases the collecting region may occur axially spaced fromthe bite or indent. The collet region 102 may in some case be furthercharacterized by a convex profile that swages the tube end.

The relative axial translation between the two fitting components 12, 16is performed so that the forward tapered surface 82 of the cartridge 76contacts and cams against the second tapered surface 94 of the body 12.The contact between the cartridge 76 and the v surface 94 produces acoining like action so that the cartridge tapered surface 82 forms astrong fluid tight seal against the camming surface 94. At the sametime, the front ferrule surface, especially at the radius 34, forms aseal against the first camming surface 92. The front ferrule 20 mayoptionally swage or bite into the tube wall S to provide tube grip.

The primary functions of the ferrules 20, 22 are to create fluid tightseals and tube grip, along with resistance to fatigue from outboardsystem induced vibration. The front ferrule 20 is used primarily toprovide a fluid tight seal against the body 12 and the tube outersurface S, while the back ferrule 22 is used for a back-up seal againstthe tube outer surface S and to provide excellent tube grip. Theparticular geometry and operation of the ferrules, or a single ferrulein such applications, can be selected as required for a particularapplication and dependent on the types of materials being used. The backferrule 22, for example, may be provided with one or more recesses inthe interior cylindrical wall 42 of the ferrule, and the driven surface62 of the ferrule may be contoured. Still further, one or both of theferrules 20, 22 may be case hardened, for example by a low temperaturecarburization process to provide very hard ferrules that are corrosionresistant. The case hardening may be applied over a portion or all ofthe ferrule surface. A number of issued patents disclose such casehardening and geometry concepts that may be applied to the ferrules,such as U.S. Pat. Nos. 6,629,708; 6,547,888; 6,165,597; and 6,093,303issued to the assignee of the present invention, the entire disclosuresof which are fully incorporated herein by reference, as well as PCTInternational Publication Nos. WO 02/063195A2 and WO 02/063194A3 alsoincorporated herein by reference. Such patents and the concepts therein,however, are exemplary in nature as to the present invention and shouldnot be construed in a limiting sense. Many different case hardeningprocesses and a wide variety of geometric configurations may be used toproperly control the plastic deformation of the ferrules during pull-upto assure adequate seal and tube grip.

Under elevated pressures, for example 15 ksi, the tube wall will tend tobe radially expanded, pushing outward on the ferrules 20, 22. Thecartridge 76 serves to radially contain the ferrules 20, 22 and preventloss of seal and tube grip. Note that the body 12 does not constrainmuch if any of the front ferrule 20. The stress of containing the frontferrule 20 radially under pressure is achieved by the cartridge 76, asis the case with the back ferrule 22. This is significant for reasonsthat will be discussed hereinbelow. Note further, particularly in FIG.1, that the optional work hardened exterior 81 will also function tocontain higher pressure by radially constraining and supporting thecartridge 76 in an assembled condition.

Upon pull-up, when the cartridge 76 engages the second camming surface94 in the body 12, not only will the cartridge form a seal against fluidpressure, but the assembler will also notice a sharp and dramaticincrease in pull-up torque. FIG. 9 is a graph of illustrative data fortorque versus nut 16 displacement. Note that in region A the torquerises somewhat slowly and steadily as a result of the ferrules 20, 22plastically deforming while biting into the tube T and camming againstthe body camming surface 92 and the front ferrule camming surface 38. Assoon as the cartridge 76 contacts the second camming surface 94 in thebody 12, however, the torque in region B increases sharply anddramatically. By selecting an appropriate torque value that correspondsto proper pull-up, the fitting 10 can be pulled-up by torque rather thanby turns. Thus, a simple torque wrench can be used to make-up thefitting 10. Note from FIG. 9 that the cartridge concept provides a verytight or steep torque to nut displacement ratio. This is in significantcontrast to prior fittings wherein the torque gradually increases as theferrules deform. Since too many factors can influence the gradual torquereadings, torque cannot always be used to accurately gauge properpull-up of prior fittings. Instead prior fittings typically arepulled-up by counting turns or displacement of the nut relative to thebody. For example, region A in FIG. 9 shows that torque can increaserather little over significant displacement of the nut relative to thebody, thus preventing torque from correlating well with turns ordisplacement.

Angling the camming surface 94, such as at the angle ρ, allows thefitting 10 to be re-made. Each remake of the fitting 10 progresses thecartridge subassembly further into the body for each re-make, even ifonly slightly. For very sharp torque increases, the angle ρ may approachninety degrees (relative to the axis X). This alternative arrangementwould provide a dramatic increase in torque for pull-up by torque, butin some cases may lessen the ability to remake the fitting 10 after theinitial pull-up.

Referring to FIG. 8, as well as the alternative embodiment of FIGS. 14and 21 for example, the contact between the cartridge forward surface 82and the body tapered surface 94 to effect pull-up by torque alsoproduces a radial support of the body for the cartridge after pull-up.This feature of these embodiments when used further facilitates the useof the fitting at higher pressures along with the pull-up by torquefunctionality.

Other embodiments may be used to effect pull-up by torque rather thanhaving the cartridge 76 engage the body 12. For example, a ferrule canbe designed to engage the body in a manner to effect pull-up by torque,as described below with regard to FIGS. 19-20. In addition, any twogenerally radial surfaces of the nut 16 and the body 12 can be designedto engage upon proper pull-up of the fitting 10 to provide the sharptorque increase. For example, an exterior surface on the fitting bodymay be designed to engage an exterior surface of the nut upon completepull-up. These surfaces, as with the camming surface 94 and cartridgetapered surface 82, may be angled to allow for remake of the fitting.

A fitting in accordance with the invention may be used in pressureapplications below 12 ksi, even 8 ksi, but more notably may be used as ahigher pressure rated fitting above 8 ksi, even above 12 ksi. A numberof features and aspects of the invention relate to the ability of thefitting to withstand higher rated pressures, as will now be discussed.

Unlike traditional female style fittings, the invention provides afitting 10 in which the ferrules 20, 22, and especially the frontferrule 20, are radially constrained against pressure by the malefitting component rather than the female fitting component. In otherwords, the front ferrule 20 engages with the camming surface 92 in amanner similar to prior female fitting designs, but is radiallyconstrained and held against pressure by the cartridge 76.

For fittings that are made of stainless steel, the nut 16 can be a workhardened part, such as can be machined from bar stock, for example,because it must be strong enough to constrain the ferrules 20, 22 underhigher pressures. The female body 12, however, does not need to be aformed from work hardened material because it is not necessarilyutilized to protect the ferrules 20, 22 under pressure. Therefore, thebody 12 may be formed from an annealed material, such as by forging orcasting, for example. Forming the fitting body 12 by forging or casting,for example austenite stainless steel, can be significantly lessexpensive than forming it by machining from hardened bar stock. This isespecially true if the fitting body is (or is part of) a complex shape,such as a tee or an elbow. As a result, significant cost savings can berealized with the present invention. Further, austenite stainless steel,which cannot be hardened by heat treating, can be utilized to form thebody without needing to work harden the steel. Forming the body fromaustenite stainless steel is advantageous in many applications due toits excellent corrosion resistance.

The ability to provide a fitting 10 that can function at higher pressurerating or working pressures with an annealed body also greatly expandsits available applications. For example, the fitting body 12 can beformed by providing a female port in a variety of fluid components thatare made of softer annealed metals, such as pump housings, cylinderheads, manifolds, tanks, and so on. Still a further alternativeembodiment, however, provides that the body 12 may also be formed fromwork hardened material or have a portion of the body work hardened, ifso required, particularly for even higher pressure ratings or workingpressures.

Selectively work hardening a portion of the fitting body 12 makes thefitting withstand high internal pressures without deformation or damagethat would cause leakage of the fitting 10. Thus, selectively workhardening the fitting body provides a similar advantage to not utilizingthe body to protect the tube gripping device 20, 22 under pressure.Specifically, the body 12 may be formed from an annealed material,rather than hardened bar stock. Doing so results in a fitting 10 thatcan function at higher pressure rating or working pressures but berealized at a significant cost savings over prior high pressurefittings.

If, for example, the fitting 10 is to be rated at 15 ksi, then it is, byindustry convention, tested typically under hydraulic pressure up to andexceeding four times that pressure rating (a 4-to-1 tube gripperformance factor), or 60 ksi. A statistically significant number offittings are tested up to and exceeding 60 ksi to reliably predict withhigh confidence that the fitting will go to at least four times theprospective working pressure without leakage. Applicants have found thatthe fitting 10 in accordance with the present invention can holdpressures up to about 75 ksi and greater, thus providing at least a5-to-1 tube grip performance factor. Thus, selectively work hardening aportion of the fitting 10 also allows the use of a relatively softforging for the fitting body 20.

As described hereinabove, the fitting 10 may be selectively workhardened by plastically deforming a portion 81 of the fitting. A portionof the fitting 10, radially outward of the ferrules 20, 22, is workhardened by rolling a set of circumferential ribs or an external malethread 98 on the fitting body 12. The work hardening can be performedconcurrently with the machining of the fitting body 12 or other part.Specifically, a piece, such as the fitting body 12, is typicallymachined on a multiple spindle machine having multiple index positionsat which various machining operations are done sequentially. With one ofthese operations being the rolling of the ribs or thread 98, to workharden the fitting body 12, the body need not be subjected to a separatework operation (off the one machine) to harden it. The part 12 can beloaded once onto the machine, machined including the work hardening toform the thread 98, then unloaded.

In addition, the male thread 98 that may be formed in the work hardeningprocess can provide a more useful configuration to the fitting 10. Inparticular, the thread 98 can be used to attach certain fittingenhancements to the fitting 12. For example, one or more lock nuts canbe threaded onto the male thread 98 to further strengthen the fitting10. Additional examples can include using the thread 98 to mount thefitting body 12 to a panel or to attach a means that can support thetube T, assist retaining the tube in the fitting 10, assist attenuatingthe effects of outside tube vibration, or other functions.

The higher pressure rating, 15 ksi or higher, may be further achievedwith the fitting 10 disclosed herein because of the ability to caseharden or carburize the ferrules. This allows the ferrules 20, 22 tobite and seal against work hardened conduits such as for example heavywalled tubing or ⅛ hard or strain hardened material that is needed forhigher pressure applications. The fitting 10 provides a back ferrule 22that has substantial bulk material to make the ferrule stronger ingripping the conduit as well as being able to bite into the conduit.Still further, the seal formed by the cartridge 76 against the secondcamming surface 94 provides a secondary or backup seal to the body sealformed by the front ferrule 20 against the first camming surface 92. Thecartridge seal against the second camming surface 94 may be facilitatedby use of the softer annealed body.

The invention, however, is not limited to use with stainless steelmaterials. For example, the automotive industry, especially foralternative fuel vehicles, may decide to pursue carbon steel rather thanstainless steel for various fittings and conduits. The inventionprovides advantages in the use of carbon steel as well, even thoughcarbon steel can be hardened by annealing. These advantages include butare not limited to the cartridge concept for easier assembly (to bedescribed further hereinbelow), providing a seal with the cartridgeagainst the body, and providing a fitting that can be pulled up totorque rather than by turns.

FIG. 10 is a longitudinal cross section of the nut 16 and two ferrules20, 22 of the exemplary fitting shown in FIG. 1 where nut and twoferrules are installed on a tool 103. The tool 103 provides a convenientway to hold the cartridge nut 16 and one or more ferrules 20, 22together as a single assembly 78 prior to make-up of a fitting 10. Thus,the assembly 78 and tool 103 together provide a single unit 104 that canbe installed in a mating fitting component, such as for example thefemale fitting component 12, so that an assembler only needs to handletwo fitting parts. As a result, there are no loose ferrules to assemble,and the ferrules can be installed at the manufacturer to avoidinstallation errors. Other techniques for providing a cartridge nutassembly such as the use of an adhesive have been described hereinabove.

FIG. 11 illustrates a perspective of an exemplary embodiment of the tool103. With reference to FIGS. 10 and 11, the tool 103 includes a head 105that can be manually gripped or can be gripped by a simple tool such aspliers. The tool 103 is a single plastic element but other materials maybe used as required. Flexible fingers 106 a and 106 b extend from thehead 105 and include at their respective distal end, a raised lip 107 aand 107 b. The lips 107 a,b and head 105 define a slot or carriage 108onto which the cartridge nut 16 and the ferrules 20, 22 can beinstalled. The flexible fingers 106 a,b radially compress enough toallow the nut 16 and then the ferrules 20, 22 to move over the lips 107a,b toward the head 105. Once past the lips 107 a,b, the fingers 106 a,bsnap back outward, thus retaining the ferrules 20, 22 and nut 16together on the tool 103 as a single assembly 78.

FIGS. 12A and 12B illustrate various steps in the use of the tool 103 tomake up the fitting 10. To make up the fitting 10, the assembly 78 isinserted into the female body 12 and the assembler can easily use fingerpressure to rotate and threadably engage the nut 16 and the body 12 (orrotate the nut into a female port in another body). As the nut 16 isthreaded into the body 12, the lips 107 a,b will engage a surface insidethe body 12, in this case the first camming surface 92. Further axialdisplacement of the assembly 78 and tool 103 into the body 12 causes thefingers 106 a,b to be radially compressed due to a camming actionagainst the body 12.

The continued axial displacement of the assembly 78 and tool 103 causesthe fingers 106 a,b to compress sufficiently for the lips 107 a,b to bedimensionally smaller than the inside diameter of the ferrules 20, 22and the nut 16. The tool 103 thus self disengages from the ferrules.When this occurs, the tool 103 can be easily extracted from the assembly78 and body 12. Note that the tool 103 can be easily adapted to any sizefitting, and also can be color coded or provided with other indicia toindicate information about the assembly 78, such as the size, materials,pull-up torque and so on. For example, a groove 109 or other suitablemarking, indicia or structure may be provided on the tool 103 to providea visual indication to the user that the fitting has been adequatelymade up in the finger tight position to allow easy removal of the tool.

FIGS. 13-18 illustrate another exemplary fitting of the presentinvention. Many of the functional features of this embodiment aresimilar to the above embodiment except as otherwise noted. The exemplaryfitting 110 of FIGS. 13-18 includes a female threaded body 112 and amale threaded nut 114. The body 112 includes a first camming surface 116and a second camming surface 118. The second camming surface 118 engageswith an angled surface 120 on the interior end 122 of a cartridge 124formed as part of the nut 114 during pull-up (FIG. 14). The angle θ ofthe surface 120 may be about forty-five degrees relative to the centrallongitudinal axis X of the fitting 110, but other angles may be used asrequired. In this embodiment, however, the cartridge 124 includes atapered or conical wall 126 that forms a tapered socket 128 for a backferrule 130 and at least a portion of a front ferrule 132. The taperedsocket 128 provides for easier withdrawal of the nut 114 duringdisassembly because the ferrules can disengage from contact with thewall 126 during withdrawal of the nut. The wall 126 may taper at anangle ε of about five to about twenty degrees relative to a centrallongitudinal axis X but other angles may be used as required. The backferrule 130 may include a tapered outer wall portion 134 to facilitatedisassembly, and the front ferrule 132 may also include a tapered outerwall portion 136. The back and front ferrule tapered outer walls 134,136 may be formed at an angle suitable to achieve the desired effect,for example, about five to about twenty degrees relative to the axis X,but other angles may be used as needed. Thus, the invention contemplatesa cartridge design in which upon disassembly the entire assembly of thenut 114 and two ferrules 130, 132 can be withdrawn or where the nut canbe separately removed. The inclusion of a tapered socket may beespecially useful for higher pressure applications because the ferruleswill not bind or “weld” to the socket wall upon pull-up or applicationof high pressure. The ferrules will disengage from the tapered socketwall as the nut is withdrawn so that torque will not be applied to theferrules during disassembly. This will help assure that a proper remakeof the fitting can be effected.

FIGS. 19 and 20 illustrate another embodiment of the present inventionwherein FIG. 19 is a longitudinal cross-section of a fitting in a fingertight position and FIG. 20 illustrates the fitting in the pulled-upposition. In this embodiment the fitting 150 includes a nut 152 and body154 that may be similar in design to the embodiments described hereinabove. In this embodiment, however, the axial length 155 of thecartridge 156 is shortened because the cartridge 156 is only being usedto retain the back ferrule 158. The front ferrule 160 is no longercontained within the cartridge 156. A tool, similar to the tool shown inFIGS. 10-12, may be used to maintain a single component assembly as inthe above described embodiments.

In this example, the front ferrule 160 includes an enlarged radiallyextending flange 162. The flange 162 is sized to fit within a bore 164of the fitting body 154. The flange 162 further includes a driven rearsurface 166 and a seal surface 168 at a forward portion 169 of theflange. The seal surface 168 extends at an angle θ, such as aboutforty-five degrees, for example. The seal surface 168 engages a firstcamming surface 170 of the body 154 during pull-up. This provides adependable secondary pressure seal and pull-up to torque design similarin function to the engagement of the front end of the cartridge of theabove embodiments.

The driven surface 166 in this example is generally radial and engagesthe front end 172 of the cartridge 156 during pull-up so that thecartridge directly drives the front ferrule 160 forward. The backferrule 158 also drives the front ferrule 160 forward until thecartridge 156 engages the front ferrule flange 162. The front ferrule160 further includes a tapered nose portion 174 that engages a secondcamming surface 176 of the body 154. The flange 162 may be appropriatelydimensioned so that the flange is supported by the body wall 178,particularly under pressure. The body 154, thus, may be formed of workhardened raw material, or may have work hardening selectively applied toan annealed body.

FIG. 21 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in the finger tight condition. Inthis embodiment, the fitting 180 includes a body 182 and ferrules 184,186 that may be similar in design to the embodiments describedhereinabove. In this embodiment, however, fitting 180 includes adifferent nut 188. The nut 188 has a generally cylindrical configurationthat defines a passage 190 for receiving a tube end T. The nut 188 hasan external thread 192 for engagement with the internal thread 194 of afemale fitting component, such as the fitting body 182, for example. Thenut 188 has a rear face or outer face 196 that includes a key hole 198.The key hole 198 is adapted to receive a key tab 200 of a keyed wrench202.

With reference to FIG. 22, the keyed wrench 202 has an elongated handleportion 203 with a generally rectangular cross-section. Thecross-sectional shape of the handle portion 203 can be other thanrectangular. For example, the handle portion 203 could have an oval orcircular cross section. The key tab 200 extends from the handle portion203 at about a right angle. The key tab 200 may extend from the handleportion 203 at an angle other than a right angle, though a right angleis preferred. The key tab 200 is adapted to mate with the key hole 198to allow the key wrench 202 to rotate the nut 188 sufficiently to pull-othe fitting 180.

The key wrench 202 also includes a clearance opening 204 extending alonga central axis 206 of the handle portion 203. The clearance opening 204is sized and positioned to allow the key wrench 202 to straddle theconduit and engage the nut 188 without the tube interfering.

The length of the nut 188 is selected so that, when the nut is fullyscrewed into the fitting body 182, the rear face 196 of the nut 96 isflush with the end of the body 182, or is recessed. There is no standardhex configuration projecting from the fitting body 182. As a result, thechance of inadvertent loosening or removal of the nut 188 is reducedsince the ability to disassemble the fitting 180 is restricted to onlythose personnel that have the specific keyed wrench 202. In addition,providing different positions for the key hole 198 on the nut 188 mayallow specific products (sizes, etc.) to be manufactured in combinationwith specific wrenches.

Further, because the nut 188 does not project from the fitting body 182,the assembled fitting 180 is smaller. This can be beneficial inapplications in which space is at a premium, for example, automotiveapplications. Finally, the nut 188 is also beneficial as it may allowfor cost reduction, since the complete nut can be silver plated (forlubrication of the threads 192) without the need to selectively platethe threads or to strip plating off of the hex area (as is done forstandard female nuts) for cosmetic effect. Thus, silver platting can beaccomplished by dipping the entire nut 188.

FIG. 23 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in the pulled-up condition. Inthis embodiment, the fitting 210 includes a body 212, a nut 216, andferrules 220 and 222 that may be similar in design to the embodimentsdescribed hereinabove. In this embodiment, however, body 212 includes anexterior camming surface 224 that engages a tapered surface 226 on thenut 216 upon proper pull-up. The exterior camming surface 224 may belocated on a forward end 228 of the body 212. The tapered surface 226 ofthe nut 216, tapers outward from the axis X away from the body 212. Thetapered surface 226 may be located, for example, on a tool engagementportion such as a hex portion 230.

FIG. 24 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in the finger tight condition. Inthis embodiment, the fitting 250 includes a body 252, a nut 256, and afirst ferrule 260 that may be similar in design to the embodimentsdescribed hereinabove. In this embodiment, however, the nut 256 includesan integral ferrule 262 that can either replace the first ferrule 260or, as shown in FIG. 24, function as a second ferrule. The geometry ofthe integral ferrule 262 (such as, for example, a tapered outer surfaceportion 264, radius portions 266 and 268, a nose portion 270, and so on)is selected so as to effect an appropriate radially inward hingingaction of the integral ferrule in response to the nose portion beingdriven into a camming surface, such as a camming surface 272 on arearward portion 274 of the first ferrule 260. The concept of a integralferrule utilized in a fitting has been disclosed in InternationalPublication Number WO 02/063194A2, the entire disclosure of which isfully incorporated herein by reference. The publication and the conceptstherein, however, are exemplary in nature as to the present inventionand should not be construed in a limiting sense.

FIG. 25 is a half longitudinal cross-section of another exemplaryfitting of the present invention shown in the finger tight condition. Inthis embodiment, the fitting 280 includes a body 282, a nut 286, and afirst ferrule 290 that may be similar in design to the embodimentsdescribed hereinabove. In this embodiment, however, the nut 286 includesa separable ferrule 292 that can either replace the first ferrule 290or, as shown in FIG. 25, function as a second ferrule. The separableferrule 292 is attached to the nut 286 by a frangible web portion 294.Upon partial pull-up of the fitting 280, the separable ferrule 292engages a camming surface, such as a camming surface 296 on a rearwardportion 298 of the first ferrule 290, and breaks off or separates fromthe nut 286. Once separate, the separable ferrule 292 functions similarto the ferrules described in the embodiments hereinabove. The concept ofa separable ferrule utilized in a fitting has been disclosed inInternational Publication Number WO 02/063195A2, the entire disclosureof which is fully incorporated herein by reference. The publication andthe concepts therein, however, are exemplary in nature as to the presentinvention and should not be construed in a limiting sense.

The invention has been described with reference to the preferredembodiments. Modification and alterations will occur to others upon areading and understanding of this specification. It is intended toinclude all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. A conduit fitting, comprising: a firstfitting component adapted to receive a conduit end along a central axis;a conduit gripping device; a second fitting component that can be joinedto said first fitting component, said second fitting componentcomprising a portion that engages a tapered surface of said firstfitting component when the conduit fitting is pulled up; said secondfitting component comprising a socket that receives said conduitgripping device, said engagement providing radial constraint of saidconduit gripping device, wherein said first fitting component comprisesa first tapered surface and a second tapered surface, with a step thatjoins said first tapered surface and said second tapered surface, saidsecond tapered surface comprising said tapered surface that engages saidportion of said second fitting component when the conduit fitting ispulled up.
 2. The conduit fitting of claim 1 wherein said second fittingcomponent radially constrains said conduit gripping device after theconduit fitting is pulled up.
 3. The conduit fitting of claim 1 whereinsaid conduit gripping device comprises a front ferrule and a backferrule.
 4. The conduit fitting of claim 2 wherein said socket retainssaid back ferrule and at least a portion of said front ferrule.
 5. Theconduit fitting of claim 1 wherein said engagement between said portionof said second fitting component and said first fitting componenttapered surface radially constrains said second fitting component andsaid conduit gripping device.
 6. The conduit fitting of claim 1 whereinsaid engagement between said portion of the second fitting component andsaid tapered surface of the first fitting component causes the amount oftorque required to continue pulling-up the conduit fitting to sharplyincrease.
 7. The conduit fitting of claim 1 wherein said first fittingcomponent comprises a camming surface that engages said conduit grippingdevice when the conduit fitting is pulled up, and said engagementbetween said portion of the second fitting component and said taperedsurface of the first fitting component occurs after said conduitgripping device engages said ferrule camming surface.
 8. The conduitfitting of claim 1 wherein said first fitting component and said secondfitting component are threadably joined together when the conduitfitting is pulled up.
 9. The conduit fitting if claim 1 wherein saidsecond fitting component comprises a socket, said socket comprising adrive surface that contacts a driven surface of said conduit grippingdevice when the conduit fitting is in a finger-tight position, saidsocket comprising a tapered surface that radially constrains saidconduit gripping device when the conduit fitting is pulled up.
 10. Theconduit fitting of claim 1 wherein said engagement between said portionof said second fitting component and said tapered surface of said firstfitting component allows the conduit fitting to be pulled up by a torqueapplied between said first fitting component and said second fittingcomponent.
 11. The conduit fitting of claim 10 wherein said torquecauses a relative axial displacement between said first fittingcomponent and said second fitting component past a finger tight positionand that corresponds to a completed pull-up of the conduit fitting. 12.The conduit fitting of claim 1 wherein said second tapered surface andsaid second fitting component portion each have an axial length and areradially tapered relative to the central axis.
 13. The conduit fittingof claim 1 wherein said step surface comprises a radial step.
 14. Theconduit fitting of claim 5 wherein said conduit gripping devicecomprises a front ferrule and a back ferrule.
 15. The conduit fitting ofclaim 9 wherein said conduit gripping device comprises a front ferruleand a back ferrule.
 16. A conduit fitting, comprising: a first fittingcomponent adapted to receive a conduit end along a central axis; aconduit gripping device; a second fitting component that can be joinedto said first fitting component, said second fitting componentcomprising a portion that engages a tapered surface of said firstfitting component when the conduit fitting is pulled up; said secondfitting component comprising a socket that receives said conduitgripping device, said engagement providing radial constraint of saidconduit gripping device, wherein said first fitting component comprisesa ferrule camming surface, said conduit gripping device comprises afront ferrule and a back ferrule, and said first fitting componenttapered surface and said ferrule camming surface are surfaces formed onthe first fitting component and are stepped from each other in aradially extending direction.